如何在Python中调用类的实例？ [英] How do you call an instance of a class in Python?

问题描述

这受到我刚刚看到的一个问题的启发，该问题是通过调用类实例来更改返回的内容，但是很快就得到了 __ repr __ 的回答（并且被接受，所以提问者

This is inspired by a question I just saw, "Change what is returned by calling class instance", but was quickly answered with __repr__ (and accepted, so the questioner did not actually intend to call the instance).

现在可以像这样调用类的实例：

Now calling an instance of a class can be done like this:

instance_of_object = object() 
instance_of_object()

但我们会收到错误消息，例如 TypeError：'object'对象不可调用。

but we'll get an error, something like TypeError: 'object' object is not callable.

此行为在CPython 此处的源中定义。

This behavior is defined in the CPython source here.

因此，请确保我们在Stackoverflow上遇到以下问题：

So to ensure we have this question on Stackoverflow:

您如何真的在Python中调用了一个类的实例？

How do you actually call an instance of a class in Python?

推荐答案

您调用了一个类的实例如下所示：

You call an instance of a class as in the following:

o = object() # create our instance
o() # call the instance

但这会通常会给我们一个错误。

But this will typically give us an error.

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: 'object' object is not callable

如何按预期方式调用实例

How can we call the instance as intended, and perhaps get something useful out of it?

我们必须实现Python特殊方法 __ call __ ！

We have to implement Python special method, __call__!

class Knight(object):
    def __call__(self, foo, bar, baz=None):
        print(foo)
        print(bar)
        print(bar)
        print(bar)
        print(baz)

实例化课程：

a_knight = Knight()

现在我们可以调用类实例：

Now we can call the class instance:

a_knight('ni!', 'ichi', 'pitang-zoom-boing!')

其中会打印：

ni!
ichi
ichi
ichi
pitang-zoom-boing!

我们现在已经成功地将称为课！

And we have now actually, and successfully, called an instance of the class!

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